From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4C7A4D46943 for ; Wed, 21 Jan 2026 14:47:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iStF1+0UpaSNBxFtH2LAPTY4dVGLGH3AvGpTjjJnIHU=; b=g5NN1d+Ka4MgIg8U1N7+u47fLA 0aOWXLaaFZw4X5sxCLinjpWKJAfjaDisbw7s+pGYhhA2POZ/5m/bBF/9v3u7i05GFFbSN+gqnXcMH 0zWP2ETOxO5eJi7iWlrak0nnT8qYDUwmveaNv291iLWK9xSQ0GoBI54i5wkzWp4lv6Ws9qfTig1+k uybrbKeOmlRSfmSvB5eejCAMYb46vvgUwR9SAKu9LMnWvgpOYBxy8TXGd+vlH8dqAQYIN9L0mwh7m VAiH99xN0b+O/wsIHVDMfWyUDtHFF2G+sjjjjI31Sfc9DblS4AFYUQ5UOJo0Ba553a35B6YWHiy68 r/iMAgGg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1viZU5-00000005dCz-3wcK; Wed, 21 Jan 2026 14:47:01 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1viZTz-00000005d5O-0gWn; Wed, 21 Jan 2026 14:46:57 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=iStF1+0UpaSNBxFtH2LAPTY4dVGLGH3AvGpTjjJnIHU=; b=e9bH30XyD6pkMJHTgoZwJ7SBsQ 0CLCJyQaHxcYuc61vX87CjlwIjH755e5RfCQJ0Wfv4lNRlzSX2yX9k/kwo8QWMtpWhfVnPgANvDB9 kl123aZe/rSEj8KpIBeh0lPIAMVOWTc19dGF+NdztKgvvnA+5BX7opil0piY56CwJO20tSmz1Xlko pzBMbMVUUyaGXSsIrFSc5JdeRIYiwiAV1GpaVlXdZ0VTRxn+jcebBR5roWfde62EU7wcfzvg9tR3Q 9GmdzF0i47FizmPYPrE1/KUuNR/fwPn0E/d24rqa7i7R6bhkesWWIr0GN+RCRzFGiFUEkdThXAtTj trX0GOiA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:36082) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1viZTt-000000007c8-10Ub; Wed, 21 Jan 2026 14:46:49 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1viZTm-0000000005o-2xDz; Wed, 21 Jan 2026 14:46:42 +0000 Date: Wed, 21 Jan 2026 14:46:42 +0000 From: "Russell King (Oracle)" To: Vladimir Oltean Cc: Jakub Kicinski , linux-phy@lists.infradead.org, davem@davemloft.net, maxime.chevallier@bootlin.com, alexandre.torgue@foss.st.com, mohd.anwar@oss.qualcomm.com, neil.armstrong@linaro.org, hkallweit1@gmail.com, mcoquelin.stm32@gmail.com, netdev@vger.kernel.org, edumazet@google.com, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, vkoul@kernel.org, andrew@lunn.ch, pabeni@redhat.com, andrew+netdev@lunn.ch, linux-stm32@st-md-mailman.stormreply.com Subject: Re: [net-next,05/14] net: stmmac: add stmmac core serdes support Message-ID: References: <20260119192125.1245102-1-kuba@kernel.org> <20260120081844.7e6aq2urhxrylywi@skbuf> <20260120121114.2aedgu42i2wax3yp@skbuf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260120121114.2aedgu42i2wax3yp@skbuf> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260121_064655_203989_C122F262 X-CRM114-Status: GOOD ( 23.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jan 20, 2026 at 02:11:14PM +0200, Vladimir Oltean wrote: > On Tue, Jan 20, 2026 at 10:12:46AM +0000, Russell King (Oracle) wrote: > > First, I'll say I'm on a very short fuse today; no dinner last night, > > at the hospital up until 5:30am, and a fucking cold caller rang the door > > bell at 10am this morning. Just fucking our luck. > > Sorry to hear that. > > > On Tue, Jan 20, 2026 at 10:18:44AM +0200, Vladimir Oltean wrote: > > > Isn't it sufficient to set pl->pcs to NULL when pcs_enable() fails and > > > after calling pcs_disable(), though? > > > > No. We've already called mac_prepare(), pcs_pre_config(), > > pcs_post_config() by this time, we're past the point of being able to > > unwind. > > I'm set out to resolve a much smaller problem. > > Calling it a full "unwind" is perhaps a bit much, because pcs_pre_config() > and pcs_post_config() don't have unwinding equivalents, unlike how > pcs_enable() has pcs_disable(). I don't see what API convention would be > violated if phylink decided to drop a PCS whose enable() returned an error. While pcs_pre_config() and pcs_post_config() do not have unwinding equivalents (what would they be?) the issue here is that these could have changed any state that isn't simply undone by calling pcs_disable(). For example, pcs_pre_config() could have reprogrammed signal routing, clocking, or power supplies to blocks. This already applies to Marvell DSA pcs-639x.c, where the pre/post config hooks change the power state of the PCS block (for errata handling), and the only way that gets undone is via a call to pcs_disable() which explicitly disables IRQs and power for the PCS. Its pcs_disable() isn't a strict reversal of pcs_enable(), it does more. We already declare the interface to be dead on pcs_post_config() failure, but we don't do that for pcs_enable() failure. Maybe I need to explicitly state that pcs_disable() does not directly balance pcs_enable(), but that _and_ the effects of pcs_pre_config() and pcs_post_config(). However, that itself will add to the problems. What if pcs_pre_config() and pcs_post_config() succeed but not pcs_enable()? pcs-639x needs pcs_disable() to be called, but if we require pcs_disable() to be balanced with a successful call to pcs_enable(), that messes up that driver, and pretty much makes it impossible to work around the errata. If you feel strongly about this, then the only thing I can think of doing is to move this SerDes support out of stmmac and into phylink (which is a point I already raised in the cover message) so that its failure can be dealt with at the higher level, where we can ensure that phy_power_off() is balaced with phy_power_on(). However, that means pushing even more of the stmmac specific "we need the clocks running to access registers XYZ or reset" weirdness into phylink. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!